The present invention relates to the field of contact lens cleaning and disinfecting. In particular, this invention is directed to the provision of alkyl trypsin containing multi-purpose compositions and methods for the preparation of these compositions. The invention is also directed to methods of simultaneously cleaning and disinfecting contact lenses by using alkyl trypsin and disinfectant containing multi-purpose compositions of the present invention.
Various compositions and methods for cleaning contact lenses have been described in the patent and scientific literature. Some of these methods have employed compositions containing surfactants or enzymes to facilitate the cleaning of lenses. The first discussion of the use of proteolytic enzymes to clean contact lenses was in an article by Lo, et al. in the Journal of The American Optometric Association, volume 40, pages 1106-1109 (1969). Methods of removing protein deposits from contact lenses by means of proteolytic enzymes have been described in many publications since the initial article by Lo, et al., including U.S. Pat. No. 3,910,296 (Karageozian, et al.).
Numerous compositions and methods for disinfecting contact lenses have also been described. Those methods may be generally characterized as involving the use of heat and/or chemical agents. Representative chemical agents for this purpose include organic anti-microbials such as benzalkonium chloride and chlorhexidine, and inorganic anti-microbials such as hydrogen peroxide and peroxide-generating compounds. U.S. Pat. Nos. 4,407,791 and 4,525,346 (Stark) describe the use of polymeric quaternary ammonium compounds to disinfect contact lenses and to preserve contact lens care products. U.S. Pat. Nos. 4,758,595 and 4,836,986 (Ogunbiyi) describe the use of polymeric biguanides for the same purpose.
Various methods for enzymatic cleaning and disinfecting contact lenses at the same time have been proposed. Methods involving the combined use of proteolytic enzymes and peroxides to clean and disinfect contact lenses simultaneously, are described in U.S. Pat. No. Re 32,672 (Huth, et al.). A representative method of simultaneously cleaning and disinfecting contact lenses involving the use of proteolytic enzymes and quaternary ammonium compounds is described in Japanese Patent Publication 57-24526 (Boghosian, et al.). The combined use of a biguanide (i.e., chlorhexidine) and liquid enzyme compositions to simultaneously clean and disinfect contact lenses is described in Canadian Patent No. 1,150,907 (Ludwig, et al.). Methods involving the combined use of dissolved proteolytic enzymes to clean and heat to disinfect are described in U.S. Pat. No. 4,614,549 (Ogunbiyi). The combined use of proteolytic enzymes and polymeric biguanides or polymeric quaternary ammonium compounds is described in copending, commonly assigned U.S. patent application Ser. No. 08/156,043 and in corresponding European Patent Application Publication No. 0 456 467 A2 (Rosenthal, et al.), as well as in U.S. Pat. No. 5,096,607 (Mowrey-McKee, et al.).
The commercial viability of most prior enzymatic cleaning products has depended on the use of stable enzyme tablets. More specifically, the use of solid enzymatic cleaning compositions has been necessary to ensure stability of the enzymes prior to use. In order to use such compositions, a separate packet containing a tablet must be opened, the tablet must be placed in a separate vial containing a solution, and the tablet must be dissolved in order to release the enzyme into the solution. This practice is usually performed only once a week due to the cumbersome and tedious procedure and potential for irritation and toxicity.
The use of concentrated liquid enzyme compositions in combination with a diluent to clean contact lenses has been attempted in an effort to avoid the cumbersome use of enzyme tablets. Those attempts, however, have been hampered by the fact that concentrated aqueous liquid enzyme compositions are inherently unstable. When a proteolytic enzyme is placed in an aqueous solution for an extended period (i.e., several months or more), the enzyme may lose all or a substantial portion of its proteolytic activity. Steps can be taken to stabilize the compositions. For example, stabilizing agents can protect enzymes from chemical instability problems during storage in an aqueous liquid, by placing the enzymes in a dormant physical conformation. However, the use of liquid enzyme compositions, as with the use of enzyme tablet compositions described above, still requires a separate, additional mixing step each time the lens is to be simultaneously cleaned and disinfected. Furthermore, since the amount of liquid enzyme composition placed in a diluting composition is controlled by the user, user error may result in too much or too little of the concentrate being dispensed in the diluting solution.
The following patents may be referred to for further background concerning prior attempts to stabilize concentrated liquid enzyme formulations: U.S. Pat. No. 5,281,277 (Nakagawa) and Japanese Kokai Patent Applications Nos. 92-370197; 92-143718; and 92-243215. Improved liquid enzyme compositions have been disclosed in U.S. Pat. Nos. 5,576,278, 5,604,190, 5,605,661, 5,672,213 5,718,895 and 5,723,421, all issued to Alcon Laboratories, Inc.
A number of multi-purpose compositions for cleaning, disinfecting and storing contact lenses are commercially available. The main cleaning ingredients of these products generally comprise surfactants. Soft contact lenses become soiled by collecting various debris and also by accumulated protein deposition on the lens surface. Failure to remove the protein deposits results in opacification of the lens and lens spoilage. While surfactants are used to remove debris from the lens, they are not very efficacious in removing protein deposits. Proteolytic agents, in contrast, are very effective in removing protein deposits that form on the lens over time. Thus, cleaning regimens using multi-purpose compositions comprising surfactants still require the additional step of employing a proteolytic agent to remove protein deposits.
The use of a single enzyme containing multi-purpose solution for the cleaning and disinfecting of contact lenses has been proposed in U.S. Pat. No. 5,409,546 (Nakagawa et al.) and European Patent Application No. 0 646, 641 (Nakagawa et al.). Those patents disclose compositions wherein the enzyme is in a dilute concentration, and the compositions, therefore, require no dilution step prior to use. Those compositions, however, provide limited stability of the enzyme (1 or 2 months at room temperature). The limited shelf-life of these compositions generally does not permit their commercialization.
What is needed, therefore, are multi-purpose compositions which provide a commercially viable storage/use shelf-life.